Hi Dayne411,
The major brands such as Sealy/Stearns & Foster, Simmons, and Serta (including the Beautyrest Black line) all tend to use lower quality and less durable materials in their mattresses than most of their smaller competitors that will tend to soften or break down prematurely relative to the price you pay which is why I would generally suggest avoiding all of them completely (along with the major retailers that focus on them as well such as Sleepy’s/Mattress Firm) regardless of how they may feel in a showroom along with any mattress where you aren’t able to find out the type and quality/durability of the materials inside it (see the guidelines here along with post #3 here and post #12 here and post #404 here).
You can see an example of the type and quality of the materials in a Beautyrest Black box top here and if you compare them to the durability guidelines here you will see that it includes some very low quality/density materials that would be a weak link in the mattress and could compromise the durability and useful life of the mattress much too quickly.
This is one of the oldest “tricks” or marketing tactics in the book that many of the larger chain stores use to create a false sense of urgency and commitment to help increase the odds that a potential customer will buy a mattress from them before they walk out the door.
If I was in your shoes there is no doubt that I would cancel the purchase and get a refund of your deposit and continue to look for a better quality/value mattress that would be just as suitable in terms of comfort, firmness, and PPP (Posture and alignment, Pressure relief, and your own Personal preferences) but that uses higher quality materials that would be much more durable.
Subject to first confirming that any retailer or manufacturer on the list that you wish to visit is completely transparent (see this article) and to making sure that any mattress you are considering meets your criteria and the quality/value guidelines here … the better options or possibilities I’m aware of in and around the larger Boston region are listed in post #2 here.
I’m not sure what you’ve read since you found the site but the best place to start your research is the mattress shopping tutorial here which includes all the basic information, steps, and guidelines that can help you make the best possible choice … and perhaps more importantly know how and why to avoid the worst ones.
Two of the most important links in the tutorial that I would especially make sure you’ve read are post #2 here which has more about the different ways to choose a suitable mattress (either locally or online) that is the best “match” for you in terms of “comfort” and PPP that can help you assess and minimize the risks of making a choice that doesn’t turn out as well as you hoped for and post #13 here (which I also linked earlier in this reply) which has more about the most important parts of the “value” of a mattress purchase which can help you make more meaningful quality/value comparisons between mattresses in terms of suitability (how well you will sleep), durability (how long you will sleep well), and the overall value of a mattress compared to your other finalists based on all the parts of your personal value equation that are most important to you.
Phoenix